disease

• Health


  A state of complete physical, mental and social well-being (as defined by the World Health Organization, WHO)
• Disease

  A disorder of the body or mind that negatively affects an individual's health
• Types of disease

  • Communicable
  • Non-communicable
• Communicable disease


  A disease that is passed directly between individuals, caused by a pathogen
• Pathogen

  A disease-causing organism e.g. virus, fungi, bacteria, protists
• Non-communicable disease


  A disease that cannot be transmitted between individuals, generally long lasting with a slow-onset, caused by lifestyle, environmental conditions, genetic mutations etc.
• Symptom

  A change experienced by an organism that indicates disease
• Having an illness


  Makes an individual more likely to contract another disease (weakens the immune system)
• Physical defence system within plants

  • Waterproof waxy cuticle - surface barrier preventing the entry of pathogens
  • Cellulose cell wall - further barrier against pathogens
• Chemical barriers in plants

  • Secretion of toxins to reduce damage by pests e.g. stinging nettles
  • Production of antibacterial chemicals that kill bacterial pathogens
• Chemicals produced by plants

  They produce physiological effects on the body so can be used in medicines to treat disease
• Medicines derived from plants

  • Quinine - antimalarial, bark of Cinchona sp.
  • Aspirin - painkiller, bark/leaves of Salix alba
• Importance of plant defence systems


  • Plants are producers so all organisms higher up in food chains rely upon their survival and ability to fight disease
  • Important in maintaining human food security
• Body's physical defence system

  • Skin - protective surface barrier
  • Blood clotting - platelets seal wounds preventing entry of pathogens into the blood
  • Respiratory tract - mucus traps pathogens, cilia waft mucus to the back of the throat where it is swallowed
• Body's chemical defence system

  • Tears - contain lysozyme which digests bacterial cell walls, killing bacteria and protecting the eye
  • Hydrochloric acid in stomach - acidic pH kills pathogens that are swallowed
• Immune system

  The body's defence against pathogens once they have entered the body, aims to prevent or minimise disease caused by pathogens
• Components of a vaccine

  • Dead, weakened or inactivated pathogens with their surface antigens still present
• Benefits of vaccinations

  • Herd immunity - vaccination of a significant proportion of the population gives some protection to individuals who are not immune
  • Helps to prevent epidemics and pandemics
• Drawbacks of vaccinations

  • High mutation rate of viruses changes the structure of viral antigens, making vaccines that are already available ineffective
  • Not guaranteed to work
  • Inactivated pathogens may mutate and become pathogenic
  • May cause an adverse reaction
  • Vaccination programmes are costly
• why might someone not want to do a vaccination

  • scared of needles
  • no access to healthcare
  • concerne over possible side effects
  • too young for vaccination program